Researchers here propose building a biomarker of aging based on analysis of what they term the volitome, the mix of volatile organic compounds secreted by the body. It is a reasonable suggestion. Near all such profiles of the aggregated output of cellular behavior (such as proteins in blood, or transcript levels in tissue samples) should contain reflections of the state of health and the level of cell and tissue dysfunction associated with aging or disease. Modern machine learning can quickly identify combinations of factors within this class of data that correlate with chronological age - or with biological age, as measured by mortality risk or incidence of age-related disease. The challenge then is to understand how these biomarkers connect to underlying processes of aging, as until that is known, it is hard to use them to assess potential age-slowing or rejuvenation therapies.
Our team and others have proposed a number of potential biomarkers, such as epigenetic clocks, serum N-glycans, and GDF15, associated to aging or age-related diseases. Moreover, during the last years, our group also studied the "volatilome", i.e. a set of endogenous Volatile Organic Compounds (VOCs) resulting from body's metabolism. VOCs are low-weight carbon-based molecules detectable in sweat, exhaled breath, blood, urine, and feces, and that, except for blood, are considered non-invasive diagnostic biomarkers. VOCs are involved in different physiological processes and VOCs profile may differ with age, gender, physiological status, reflecting the metabolic conditions of an individual and represents her/his "odor-fingerprint".
We wondered whether this kind of biomarkers could be useful also to identify people's age, as suggested by previous studies. We then investigated VOCs profile in healthy aging and longevity in humans by analyzing the VOCs in both urine and feces that better mirror the endogenous metabolism of the organism. The samples derived from volunteers of different age, including centenarians and their offspring that represent a sort of "super-controls" to identify potential VOCs biomarkers of successful aging and longevity. We have reported the existence of specific patterns of urinary and fecal VOCs that can discriminate subjects of different age, from young to centenarians, and, even more interesting, centenarians' offspring from age-matched controls.
Among the different VOCs identified in our study, we found that the fecal VOCs belonging to aldehydes class are less abundant in the group of young with respect to the groups of elders, that generally display a greater susceptibility to inflammation and diseases. This finding is in agreement with literature data indicating that metabolites belonging to aldehydes class are produced during inflammatory processes and are involved in several age-related diseases, such as atherosclerosis, cardiovascular diseases, neurodegenerative diseases, and metabolic disorders. These observations suggested that the different VOCs patterns may likely reflect changes in metabolic processes associated with age and health status.